Optics For Astronomy Give Humans Super Vision
Source: UniSci.com
June 12, 2000
Adapting technology originally developed by astronomers
to obtain better images of the heavens, a University of Rochester
scientist has developed an optical system that has given research
subjects an unprecedented quality of eyesight.
The research dramatically improves the sight even of
people who have 20/20 vision. Vision scientist David Williams
presented his work last week at the summer meeting of the American
Astronomical Society in Rochester, N.Y.
While the work is still in a research stage, eye-care
giant Bausch & Lomb has licensed the technology and is working with
University researchers to commercialize it.
"For years David has been way out in front exploring how
we could enhance people's vision beyond what is normally thought of as
perfect vision," says Scott MacRae, one of the world's leading cornea
specialists and a widely recognized pioneer in refractive surgery.
MacRae is moving to the University's Medical Center this
month to join Williams at the newly established Alliance for Vision
Excellence, a new collaboration between the University and Bausch &
Lomb that is dedicated to improving
technology to correct vision-impairing anomalies of the eye.
"In the old days," says MacRae, "we were just trying to
correct people's vision problems and treat disease. This new research
takes what we consider normal vision and enhances it. This is truly
revolutionary," says MacRae, who is
writing a book on such research, which he calls "the quest for super
vision."
Just last month at the annual meeting of the Association
for Research in Vision and Ophthalmology, researchers from several
laboratories and companies devoted a
whole symposium to the topic of enhanced vision.
Williams uses technology known as adaptive optics, which
was originally developed by astronomers to sharpen images from
telescopes by correcting for aberrations in the atmosphere.
Adaptive optics have been implemented on several
telescopes, including the giant Keck Telescope in Hawaii, resulting in
remarkably crisp images. Williams, who is Allyn Professor of Medical
Optics and director of the University's Center for Visual Science, has
led a decade-long effort to apply the technology to improve ordinary
human vision.
His researchers direct a harmless, highly focused spot
of light into the eye of a research subject and measure the light that
is reflected outward. That light provides a glimpse or snapshot of the
topography of the eye in exquisite detail.
The light is broken up into 217 laser beams that are
sent into a sophisticated device known as a wavefront sensor. The
sensor analyzes deviations in each beam's path, revealing tiny
imperfections or aberrations that exist in the
person's cornea and lens.
The system detects visual distortions so subtle that
physicians didn't even know they existed until Williams' laboratory
invented the system. Today a visit to the eye doctor focuses mainly on
two types of aberration: astigmatism and
defocus. Most prescriptions are intended to correct for these two
defects.
Williams' system can measure up to 65 different
aberrations.
These precise measurements are sent to a sensitive
"deformable" mirror -- a mirror that can bend and customize its shape
according to the measurements of a person's eye. Such flexible mirrors
form the heart of traditional adaptive-optics systems used in
astronomy.
The mirror in Williams' laboratory is a two-inch-wide
device that bends as little as one or two micrometers (just
one-fiftieth the width of a human hair) thanks to 37 tiny
computer-controlled pistons. This subtle shaping, done in response to
the customized measurements of a person's optical system, alters the
light in such a way that it exactly counters the specific distortions
in a person's eye.
In the laboratory, Williams' team has shown that
correcting these imperfections can result in greatly improved vision.
He has published this work in the Journal of the Optical Society of
America.
"When you look through an adaptive optics device, the
world looks crisper," Williams says. "In some people, the ability to
pick up contrast, such as minute patterns of stripes, is increased by
a factor of six. It allows for a level of vision correction that's
just not available today.
"It's like needing glasses and getting them for the
first time. Everything suddenly looks sharper and clearer, no matter
how good your eyes are normally. When you're using the adaptive optics
system, you just say 'wow.'"
Williams is an expert on the circuitry of the human
retina and the optics of the eye. After discovering some of the basic
limits of the optical system of the human eye, he began exploring ways
to improve ordinary human vision, eventually
working closely with astronomers and other adaptive-optics experts.
The research is now funded by the National Science
Foundation Center for Adaptive Optics (based at the University of
California, Santa Cruz), the National Eye Institute, and Bausch &
Lomb.
Williams has found that the visual acuity of the human
eye can be somewhere around 20/10. While adaptive optics may someday
help patients approach that level, he says that acuity isn't the most
noticeable improvement.
Adaptive optics improves eyesight most under low-light
conditions, such as night-time driving. MacRae, the laser surgery
expert, estimates that a driver sharing the road with a bicyclist at
dusk could see the bicyclist from roughly twice as far away if he or
she were equipped with adaptive optics correction.
In the past, Williams has used the system to look into
the eye. In a series of papers in such journals as Nature, Williams'
team has published the best images ever obtained of the living human
retina. Last year the team was able to differentiate the three types
of cones in the living human retina. Detailed information on the eye
is helpful to ophthalmologists monitoring patients with diseases such
as age-related macular degeneration or diabetic retinopathy.
While the current set-up is too bulky to bring the
experience of enhanced vision or super vision to many patients, MacRae
is confident that that day is not too far off.
"Someday you may no longer have to sit and answer
patiently when you're asked repeatedly whether lens No. 1 or lens No.
2 is better," MacRae says. "Someday you may just look into a wavefront
sensor such as David has developed, and in
one quick second we'll have all the information needed to improve
someone's vision dramatically."
by Tom Rickey
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